(1) Field of the Invention
The present invention relates to a sliding member including a steel back metal and a sliding layer.
(2) Description of Related Art
Sintered copper based materials having a porosity of approximately 5 to 25% have been conventionally used for a sliding member of a fuel injection pump. A liquid fuel is supplied from an outer surface side of a cylindrical sliding member to an inner surface (sliding surface) side through pores in the sliding member, so that a lubricating fluid film of the liquid fuel is formed on the inner surface (sliding surface) to support a high-speed rotating shaft. Such sintered copper based materials have a problem that a copper alloy is subjected to corrosion due to organic acids or sulfur included in the fuel, and then the copper based corrosion products contaminate the fuel. For the reason, sintered copper based sliding materials including Ni, Al and Zn have been proposed to improve the corrosion resistance (see e.g. JP-A-2002-180162, JP-A-2013-217493 or JP-A-2013-237898).
On the other hand, sliding members made of multi-layered sliding materials have been conventionally used. The multi-layered sliding materials include a porous sintered layer of a copper alloy provided on a surface of a steel back metal through a copper-plated layer. Pores and a surface of the sintered layer are impregnated and covered with a resin composition (see e.g. JP-A-2002-61653 or JP-A-2001-355634). It has been proposed to apply such multi-layered sliding materials to a sliding member of a fuel injection pump (see e.g. JP-A-2013-83304).